Electric lamp device



Oct. 29, 19 w. FREATAG ET AL ELECTRIC LAMP DEVICE Filed July 7, 1931 mvmms BY M7w6 ATTOkNEY Patented Oct. 29, 194

PATENT OFFICE" memo mm D vron Willy Freitag m1 Martin Reger, Berlin,Germany,

assignors to General Electric Company, a corporation of New YorkApplication July '1, 1931, Serial No. 549,290

In Germany August 8, 1930 i 3 Claims.

The present invention relates to electric lamp devices generally andmore particularly the invention relates to such devices having anincandescent filament and a luminescent gaseous filling 6 useful as alight source, and as an ultra violet generator.

In previous devices of this type the light emitted by the incandescentfilament has drowned out the light emitted by the luminescent gaseousatmosphere so that the spectrum of the light emitted by such device wasstrong in the colors of the light emitted by the incandescent filamentand weak in the colors of the light emitted by the luminescent gaseousfilling. The object of the present invention is to provide a lamp deviceof the above type in which the spectrum of the light emitted by suchdevice is as rich in the color of the light emitted by the luminescentgas as in the color of the light emitted by the incandescent filament. Afurther object 01' the invention is to provide such a device in whichthe filament consumes less current than in prior devices of the sametype. A still further object of the invention is to provide such adevice having a long operating life. Still further objects attaching tothe device and to its use and operation will be apparent to thoseskilled in the art from the following particular description and fromthe claims.

Inaccordancewith these objects the device comprises a metal filamenthaving electron emitting material in operative relation therewith,either impregnated therein or coated thereon. The elec- 85 tron emittingmaterial makes possible the ionization of the gaseous atmosphere in thecontainer of the device at a lower temperature of the filament than insuch devices having a filament consisting solely of high melting pointmetal alone. Since the filament operates at a low temperature it has along operating life and the color and intensity of its emitted lightdoes not drown out the light emitted by the luminescent gaseousatmosphere.

In the drawing accompanying and forming part of this specification anembodiment of the invention is shown in side elevation.

Referring to the drawing the lamp device comprises a glass container Ihaving therein a stem 60 3. Screw base 2 is attached to said containerI. Two current leads 5 are sealed into pinch part 4 of said stem 3, saidcurrent leads 5 serving as a support for a coil shaped incandescentfilament 6. Said filament 6 is supported by wire I at- $5 tached to themid-part thereof and sealed into the pinch part 4. Said wire I is notconnected into the circuit.. The container l is filled with the usualdischarge conducting gases well known in the art such as, for example,argon, helium, neon, nitrogen or carbon dioxide. An especially good,filling is a mixture of argon and helium at a pressure of 3 mm. A smallquantity such as 1 gram or several' grams, of a vaporizable materialsuch as mercury is introduced into the tube and forms, as shown, a smalldrop or body 8. The vaporizable metal may also be in the form of acoating on the interior of the lamp chamber according to the materialused. Sodium, potassium, cadmium, or magnesium may be used as thevaporizable metal if desired. The incandescent filament 6 consists of ahigh melting point metal,

such as tungsten, coated with electron emitting material. The electronmaterial may also be mixed in pulverized form with the metal of theincandescent filament during the making of said filament ii desired.Instead of the electron emitting material being impregnated in thefilament, it can also be a rod surrounded by the filament or a tubesurrounding or surrounded by the filament. Such materials as the oxidesof alkali or earth alkali metals are suitable for use as the electronemitting material.

when current is applied to the device the vaporizable material, pool 8,is vaporized by the heat radiations from the filament 6, and at the sametime the filament 6 emits a heavy stream of electrons which ionizes thegas, argon and helium, in the container I. Due to the potentialdifference of leads 5 an electric discharge parallel tothe filament 6 isformed, supported by the ionized principal rare gas filling. Thisgaseous discharge excites the metal vapor, as is well known in'the art,and brings said vapor to an -intensive luminescence, so that the lightoutput of the principal gas filling is drowned out.

In previous lamps of this type it was necessary to heat the filamentto-a temperature of 2,000 C. to obtain a discharge current of 100milliamperes and to a temperature of 2400 C. up to 2500 C. to obtain adischarge current of /2 ampere; in the present invention, due to theelectron emitting material of the filament, it is sufficient if thefilament is heated only to 800 to 900 C. to'obtain a discharge currentof 100 milliamperes and only to 1100 to 1200" C. to obtain a dischargecurrent of ampere. Therefore less current is consumed by the filament inthe present device and more by the gaseous atmosprere in said device.The filament need not be brought to a white heat,-

a red heat or a yellowheat being sufiicient to ionize the gaseousfilling so thaNhe intensity and color 01 the lishLe mitted by the metalvapor filling is as strong or stronger than the light emitted by saidfilament. The lower operating temperature of the filament results in alonger life for the device..

It will be understood that the container is of quartz, uviol glass,Pyrex or lead or lime glass,

and capable of transmitting all or a portion only of the lines of thespectrum of the light, visible or invisible generated by the device, asis now well understood in the art, such as a uviol glass, having acut-oil around 2750-3000A when it is desired to use the device as anultra violet generator for health purposes.

What we claim as new and desire to secure by Letters Patent of theUnited States, is:

1. An energy emitter comprising a container, asupport therein, aconductor mounted on the support, said conductor being formed ofstraight sections positioned at an acute anglerelative to each other, acoating of electron emitting material having an emissivity greater thanthat of thorium oxide on each of said sections, and an ionizable gaswithin the container, the breakdown potential per unit length of the gasalong the sec tions of said conductor when heated being less than thepotential necessary to bring the unit filament length up to denseelectron emitting temperature.

2. An electric lamp device comprising a container, a gaseous fillingtherein, a substantially ii. An'electric lamp device comprising acontainer, a gaseous filling therein, a substantially V-shaped filamentsealed'therein, said filament comprising a high melting point metal andone or more oxides of alkaline earth metals for emitting suflicientelectrons to excite said gaseous filling in a discharge between the legs01' said V-shaped filament, said filament constituting the sole terminalsource of the discharge, said gaseous filling comprising a mixture ofinert gas and a metal vapor.

W'ILLY FREITAG. MARTIN REGER.

